ACU193, a Monoclonal Antibody that Selectively Binds Soluble Aß Oligomers: Development Rationale, Phase 1 Trial Design, and Clinical Development Plan.

BACKGROUND: Alzheimer's disease is a large and growing unmet medical need. Clinical trial designs need to assess disease-related outcomes earlier to accelerate the development of better treatments for Alzheimer's disease. ACU193 is a monoclonal antibody that selectively targets amyloid ß oligomers, thought to be the most toxic species of Aß that accumulates early in AD and contributes to downstream pathological effects. Nonclinical data indicate that ACU193 can reduce the toxic effects of amyloid ß oligomers. ACU193 is currently being investigated in a phase 1 clinical trial designed with the properties described in this report. This phase 1 trial is designed to provide data to enable a go/no-go decision regarding the initiation of a subsequent phase 2/3 study. OBJECTIVES: To design a phase 1 study that assesses target engagement and incorporates novel measures to support more rapid development of a potential disease-modifying treatment for Alzheimer's disease. DESIGN: The INTERCEPT-AD trial for ACU193 is an ongoing randomized, placebo-controlled phase 1a/b study that assesses safety, tolerability, pharmacokinetics, target engagement, clinical measures, and several Alzheimer's disease biomarkers, including novel digital and imaging biomarkers. SETTING: For INTERCEPT-AD, brief inpatient stays for patients in the single ascending dose portion of the study, with the remainder of the evaluations being performed as outpatients at multiple clinical trial sites in the U.S. PARTICIPANTS: Patients with early Alzheimer's disease (mild cognitive impairment or mild dementia with a positive florbetapir positron emission tomography scan). INTERVENTION: ACU193 administered intravenously at doses of 2- 60 mg/kg. MEASUREMENTS: Safety assessments including magnetic resonance imaging for the presence of amyloid-related imaging abnormalities, clinical assessments for Alzheimer's disease including the Alzheimer's Disease Rating Scale-cognition and Clinical Dementia Rating scale, pharmacokinetics, a measure of target engagement, and digital and imaging biomarkers, including a computerized cognitive test battery and a measure of cerebral blood flow using arterial spin labelling magnetic resonance imaging. RESULTS: A phase 1 study design was developed for ACU193 that allows collection of data that will enable a go/no-go decision for initiation of a subsequent adaptive phase 2/3 study. CONCLUSIONS: A phase 1a/b trial and an overall clinical development plan for an Alzheimer's disease treatment can be designed that maintains patient safety, allows informed decision-making, and achieves an accelerated timeline by using novel biomarkers and adaptive study designs.

What Have We Learned from Expedition III and EPOCH Trials? Perspective of the CTAD Task Force.

Although the results were disappointing from two recent clinical trials of amyloid-targeting drugs in mild-to-moderate AD, the trials provided information that will be important for future studies, according to the EU-US CTAD Task Force, which met in November 2017 to discuss the EXPEDITION3 and EPOCH trials. These trials tested two of the predominant drug development strategies for AD: amyloid immunotherapy and BACE inhibition in populations largely composed of mild AD dementia patients. The results of these trials support the emerging consensus that effective amyloid-targeted treatment will require intervention in early, even pre-symptomatic stages of the disease. Further, the Task Force suggested that a refinement of the amyloid hypothesis may be needed and that other hypotheses should be more fully explored. In addition, they called for improved biomarkers and other outcome assessments to detect the earliest changes in the development of AD.

Analysis of the Relationship of Cognitive Impairment and Functional Impairment in Mild Alzheimer's Disease in EXPEDITION 3.

BACKGROUND: Clinical progression of Alzheimer's disease is characterized by impairment in cognition and function. OBJECTIVE: To assess the relationship between cognitive and functional impairment in mild Alzheimer's disease. DESIGN: Spearman's rank correlations between cognitive and functional measures were calculated. Autoregressive cross-lagged panel analyses were used to determine the temporal relationship between cognitive and functional decline. SETTING: Post-hoc analysis of clinical trial data. PARTICIPANTS: Placebo-treated patients with mild Alzheimer's disease from the Phase 3 solanezumab study EXPEDITION 3. INTERVENTION: Placebo. MEASUREMENTS: Cognitive and functional measures were assessed at baseline and at six post-baseline time points through Week 80. RESULTS: Correlation between cognitive and functional measures was 0.41 at baseline and 0.65 at Week 80. Autoregressive cross-lagged panel analysis demonstrated that cognitive impairment preceded and predicted subsequent functional decline, but functional scores did not predict cognitive outcomes. CONCLUSIONS: This study supports the hypothesis that functional impairment predictably follows cognitive decline in mild Alzheimer's disease dementia.

The Integrated Alzheimer's Disease Rating Scale (iADRS) Findings from the EXPEDITION3 Trial.

The Integrated Alzheimer's Disease (AD) Rating Scale (iADRS) is a composite tool that combines scores from the AD Assessment Scale-Cognitive subscale (ADAS-Cog) and the AD Cooperative Study - instrumental Activities of Daily Living (ADCS-iADL). It demonstrates acceptable psychometric properties, and is effective in capturing both disease progression and separation of placebo and active drug effect. We assessed the performance of iADRS in the solanezumab EXPEDITION3 study, an 80-week, placebo-controlled study of individuals with mild AD dementia. A statistically significant difference between placebo and active drug was observed for iADRS score change from baseline at Week 28 (p=0.028) through Week 80 (p=0.015). Across the Phase 3 solanezumab trials, iADRS was the only tool that consistently differentiated between solanezumab and placebo groups. These findings suggest that the iADRS is a useful integrated measurement tool for treatment trials of individuals with mild AD dementia.

Delayed-Start Analyses in the Phase 3 Solanezumab EXPEDITION3 Study in Mild Alzheimer's Disease.

OBJECTIVE: A delayed-start design has been proposed to assess a potential disease-modifying effect in investigational drugs for Alzheimer's disease that target the underlying disease process. We extended this methodology to recently obtained data from the EXPEDITION3. METHODS: EXPEDITION3 was a Phase 3, double-blind study with participants randomized to solanezumab (400 mg) or placebo every 4 weeks for 80 weeks, with an optional extension of active treatment. The delayed-start analysis was designed to determine if a statistically significant treatment difference established during the placebo-controlled period is maintained (at predefined level) during the delayed-start period, which would suggest the active drug has a disease-modifying effect. The delayed-start analysis was assessed across multiple efficacy measures, and includes data from baseline in the placebo-controlled period and up to 9 months in the delayed-start period. RESULTS: No significant difference was observed between the placebo and solanezumab treatment groups at the end of the placebo-controlled period for the Alzheimer's Disease Assessment Scale-Cognitive 14-item subscale. A significant treatment difference was observed at the end of the placebo-controlled period for the Alzheimer's Disease Cooperative Study-Activities of Daily Living instrumental items, an effect also seen at 6 months in the delayed-start period, and the noninferiority criterion was met. No other efficacy measures met these criteria. CONCLUSIONS: Delayed-start statistical methodology was used to understand the longitudinal outcomes in EXPEDITION3 and its extension. The small treatment differences observed at the end of the placebo-controlled phase prevented adequate assessment of any putative disease modifying effect.

Correlation between Cognition and Function across the Spectrum of Alzheimer's Disease.

BACKGROUND: Both cognitive and functional deterioration are characteristic of the clinical progression of Alzheimer's disease (AD). OBJECTIVES: To systematically assess correlations between widely used measures of cognition and function across the spectrum of AD. DESIGN: Spearman rank correlations were calculated for cognitive and functional measures across datasets from various AD patient populations. SETTING: Post-hoc analysis from existing databases. PARTICIPANTS: Pooled data from placebo-treated patients with mild (MMSE score ≥20 and ≤26) and moderate (MMSE score ≥16 and ≤19) AD dementia from two Phase 3 solanezumab (EXPEDITION/2) and two semagecesatat (IDENTITY/2) studies and normal, late mild cognitive impairment (LMCI) and mild AD patients from the Alzheimer's Disease Neuroimaging Initiative 2-Grand Opportunity (ADNI-2/GO). Intervention (if any): Placebo (EXPEDITION/2 and IDENTITY/2 subjects). MEASUREMENTS: Cognitive and functional abilities were measured in all datasets. Data were collected at baseline and every three months for 18 months in EXPEDITION and IDENTITY studies; and at baseline, 6, 12, and 24 months in the ADNI dataset. RESULTS: The relationship of cognition and function became stronger over time as AD patients progressed from preclinical to moderate dementia disease stages, with the magnitude of correlations dependent on disease stage and the complexity of functional task. The correlations were minimal in the normal control population, but became stronger with disease progression. CONCLUSIONS: This analysis found that measures of cognition and function become more strongly correlated with disease progression from preclinical to moderate dementia across multiple datasets. These findings improve the understanding of the relationship between cognitive and functional clinical measures during the course of AD progression and how cognition and function measures relate to each other in AD clinical trials.

A Combined Measure of Cognition and Function for Clinical Trials: The Integrated Alzheimer's Disease Rating Scale (iADRS).

It is generally recognized that more sensitive instruments for the earliest stages of Alzheimer's disease (AD) are needed. The integrated Alzheimer's Disease Rating Scale (iADRS) combines scores from 2 widely accepted measures, the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and the Alzheimer's Disease Cooperative Study - instrumental Activities of Daily Living (ADCS-iADL). Disease progression and treatment differences as measured by the iADRS were analyzed using data from solanezumab EXPEDITION, EXPEDITION2, and EXPEDITION-EXT Studies; semagacestat IDENTITY Study; and donepezil ADCS - mild cognitive impairment (ADCS-MCI) Study. Psychometric properties of the iADRS were established through principal component analysis (PCA) and estimation of contributions of subscores and individual item scores to the iADRS total score. The iADRS performed better than most composites and scales in detecting disease progression and comparably or better than individual scales in detecting treatment differences. PCA demonstrated the iADRS can be divided into two principal components primarily representing cognitive items and instrumental ADLs. Dynamic ranges of the subscales were similar across all studies, reflecting approximately equal contributions from both subscales to the iADRS total score. In item analyses, every item contributed to the total score, with varying strength of contributions by item and across data sets. The iADRS demonstrated acceptable psychometric properties and was effective in capturing disease progression from MCI through moderate AD and treatment effects across the early disease spectrum. These findings suggest the iADRS can be used in studies of mixed populations, ensuring sensitivity to treatment effects as subjects progress during studies of putative disease-modifying agents.

Amyloid-ß-directed immunotherapy for Alzheimer's disease.

Current treatment options for Alzheimer's disease (AD) are limited to medications that reduce dementia symptoms. Given the rapidly ageing populations in most areas of the world, new therapeutic interventions for AD are urgently needed. In recent years, a number of drug candidates targeting the amyloid-ß (Aß) peptide have advanced into clinical trials; however, most have failed because of safety issues or lack of efficacy. The Aß peptide is central to the pathogenesis, and immunotherapy against Aß has attracted considerable interest. It offers the possibility to reach the target with highly specific drugs. Active immunization and passive immunization have been the most widely studied approaches to immunotherapy of AD. A favourable aspect of active immunization is the capacity for a small number of vaccinations to generate a prolonged antibody response. A potential disadvantage is the variability in the antibody response across patients. The potential advantages of passive immunotherapy include the reproducible delivery of a known amount of therapeutic antibodies to the patient and rapid clearance of those antibodies if side effects develop. A disadvantage is the requirement for repeated infusions of antibodies over time. After more than a decade of research, anti-amyloid immunotherapy remains one of the most promising emerging strategies for developing disease-modifying treatments for AD. In this review, we examine the presently ongoing Aß-directed immunotherapies that have passed clinical development Phase IIa.

EU./U.S. CTAD Task Force on Alzheimer's Trial Populations.

Successful therapeutic trials require well-targeted populations to demonstrate the effectiveness of a drug candidate. Most trials in the field of Alzheimer's disease (AD) have been conducted in patients with mild to moderate dementia. However, the advent of amyloid PET imaging has demonstrated that a significant proportion of individuals enrolled in such studies do not have evidence of brain amyloidosis and may in fact not have Alzheimer's disease. Further, dementia represents an advanced stage of neurodegeneration, perhaps too late for significant benefits of disease-modifying interventions. The successful development of effective disease-slowing therapies requires a study population selected in accordance with the mechanism of the specific intervention. An international task force of investigators from academia, industry, non-profit foundations, and regulatory agencies met in San Diego, California, USA, on November 13, 2013, to address issues related to screening and identification of clinical trial participants, and the ramifications of decisions made in this regard for drug development in AD and other dementias.

Designing clinical trials for early (pre-dementia) Alzheimer's disease: determining the appropriate population for treatment.

Treatments that are designed to reduce Alzheimer's disease (AD) pathology may be most useful when given to subjects prior to a diagnosis of AD using current diagnostic criteria. These earlier patients may have early cognitive losses consistent with mild cognitive impairment (MCI) or may be completely asymptomatic. Screening and treatment programs for other disease states have been explored previously; these include cholesterol screening for cardiovascular disease, genetic screening for Huntington ' s disease and screening for some types of cancer. Cancer screening and treatment programs have been developed for colon cancer, breast cancer and prostate cancer. Screening programs for these other disease states are briefly reviewed and are compared to preliminary modeling data describing a hypothetical screening and treatment program for AD. While primary prevention based on screening of asymptomatic individuals using biomarkers has broad appeal, secondary prevention employing treatment of patients with MCI may be more easily implemented.

Report of the task force on designing clinical trials in early (predementia) AD.

BACKGROUND: A large number of promising candidate disease-modifying treatments for Alzheimer disease (AD) continue to advance into phase II and phase III testing. However, most completed trials have failed to demonstrate efficacy, and there is growing concern that methodologic difficulties may contribute to these clinical trial failures. The optimal time to intervene with such treatments is probably in the years prior to the onset of dementia, before the neuropathology has progressed to the advanced stage corresponding to clinical dementia. METHOD: An international task force of individuals from academia, industry, nonprofit foundations, and regulatory agencies was convened to discuss optimal trial design in early (predementia) AD. RESULTS: General consensus was reached on key principles involving the scope of the AD diagnosis, the selection of subjects for trials, outcome measures, and analytical methods. CONCLUSION: A consensus has been achieved in support of the testing of candidate treatments in the early (predementia) AD population.

The influence of matrix type, diurnal rhythm and sample collection and processing on the measurement of plasma beta-amyloid isoforms using the INNO-BIA plasma Abeta forms multiplex assay.

OBJECTIVE: The aim of the study was to determine the extent to which plasma matrix types, diurnal rhythm and sample collection and processing procedures contribute to overall variability of measurements with the INNO-BIA plasma Abeta forms assay. METHODS: Plasma samples from healthy volunteers were collected at BARC-CRI. Analyte concentrations from various plasma matrix types (EDTA, heparin, fluoride) were compared to serum after collection of blood in commercial plastic and glass tubes. Sample processing variables including time and temperature before and after centrifugation, centrifugal force and plasma dilution factor were also investigated. Diurnal variability in plasma Abeta isoforms was determined in 29 healthy volunteers by analysis of EDTA plasma specimens serially collected over 24 hours and stored frozen following oral administration of a placebo treatment. All plasma samples from a given individual and experiment were analyzed in a single analytical run. RESULTS: Highest Abeta levels were obtained using EDTA-plasma samples (in contrast to serum, heparin, citrate, or fluoride). Addition of aprotinin to EDTA plasma had no effect on Abeta peptide recovery. The elapsed time and temperature exposure, before and after sample processing affects the recovery of Abeta isoforms. Analyte recovery was not significantly affected by the presence of platelets in plasma samples. At the subject level, analysis of serially collected EDTA plasma specimens from healthy volunteers revealed no evidence of diurnal variation in any of the Abeta isoforms investigated and results from samples collected on a monthly basis showed only very limited intra-individual variation. CONCLUSIONS: Optimal recovery of Abeta peptides was obtained from blood drawn into EDTA tubes and processed within 4 h. Plasma that was refrigerated after separation and analysed within 4 h gave comparable results to samples immediately processed and frozen at -70 degrees C.

Effects of a gamma-secretase inhibitor in a randomized study of patients with Alzheimer disease.

LY450139 dihydrate, a gamma-secretase inhibitor, was studied in a randomized, controlled trial of 70 patients with Alzheimer disease. Subjects were given 30 mg for 1 week followed by 40 mg for 5 weeks. Treatment was well tolerated. Abeta(1-40) in plasma decreased by 38.2%; in CSF, Abeta(1-40) decreased by 4.42 +/- 9.55% (p = not significant). Higher drug doses may result in additional decreases in plasma Abeta concentrations and a measurable decrease in CSF Abeta.

Risky decision making in Huntington's disease.

In the clinical setting, Huntington's disease is associated with problems in judgment and decision making, however, the extent of these problems and their association with clinical characteristics have not been assessed. Recently, a laboratory-based simulated gambling task has been used to quantify similar decision-making deficits in ventromedial frontal lobe damaged participants. We hypothesized that participants with Huntington's disease (HD) would show deficits on this gambling task. For this study, 14 HD participants were asked to make 100 selections from four decks of cards with varied payoffs in order to maximize winnings of play money. They were compared to 22 participants with Parkinson's disease (PD) and 33 healthy controls. After an initial period in which participants had to learn contingencies of the decks, the HD group made fewer advantageous selections than the PD and control groups. In HD, the number of advantageous selections in the gambling task was correlated with measures of memory and conceptualization but not disinhibition. Thus, people with HD may have had difficulties learning or remembering win/loss contingencies of the decks, or they may have failed to consistently take these into account in their card selections. These findings are consistent with current models of frontal-subcortical brain circuits and behavior.